Soak the dried porcini in 200ml boiling water for 15 minutes, then drain the liquid and discard the mushrooms.
Warm the mushroom liquor in a medium-sized saucepan over a medium heat. Once it begins to bubble, add the butter and melt. Whisk through the flour and cook for 3 minutes. Whisk in the red wine and stock and stir through the marmalade, bay leaf and thyme. Bring just to the boil and bubble for 25-30 minutes or until reduced and thickened enough that it just coats the back of a spoon. Strain through a sieve and season to taste.